You're right super sapper, once maximum vacuum is achieved there would be no loss through the tap, but only if maximum vacuum has been achieved. We've got a each woods set up slightly different. One only has about 15 foot of total elevation difference, but using the 3/16 still provides an advantage compared the 5/16, and although the loss may be marginal it's still a loss. Splitting hairs here really but a good topic none the less